1. Related Applications
There are no applications related hereto heretofore filed in this or any foreign country.
2. Field of Invention
My invention relates generally to piezoelectric pressure sensors and more particularly to such a device to continuously sense the pressure of an animal foot against a reactive supporting surface, especially during locomotive activities.
3. Description of Prior Art
In dealing with the physiology of running of various animals, even including man, it is oftentimes desirable or necessary to sense the time of contact of the animal's foot or portions of it on an underlying supporting surface and also to sense the pressure between the various parts of that foot and the supporting surface. These physiological parameters may be used to indicate various systemic deficiencies and anatomical problems, especially in the lower animals, as well as to study and explain the locomotive process itself. The determination of these parameters is somewhat of a problem in the case of animals below the evolutionary standard of man because of lack of rational communication, and yet this determination is even more important in such animals as they often cannot indicate the existence of deficiencies or problems by any particular indicative reaction. Oftentimes, even in man, systemic problems may exist and may not be timely sensed, especially in their earlier stages.
This situation has long been recognized, at least since Marey's studies of the physiology of running horses in the middle 1800's. In general, however, the primary thing that has heretofore been sensed has been the relative motion of an animal's legs as oriented in time and this sensing has been accomplished largely by cinematography of one sort or another. Obviously cinematographic methods of sensing animal motion do not determine or measure the pressure of the animal's foot upon an underlying reactive surface, and particularly do not demonstrate any differential pressures over various parts of the foot.
It has heretofore become known to sense the pressure of an animal's foot and its various parts upon a supporting surface, both absolutely and differentially during locomotion. Heretofore, however, such pressure sensation has been accomplished by some pneumatic or hydraulic device and the measurements produced have generally been more qualitative than quantitative and used largely to determine the time sequence of pressure contact of a foot in relation to the time of contact of another foot or other feet. The hydraulic and pneumatic methods of measurement have generally not been particularly accurate either in time or pressure measurement because of the compressability of the measuring medium, in the case of pneumatic devices and because of the relatively slow response time and system resistivity in the case of hydraulic instruments. Generally neither the known pneumatic nor hydraulic devices have had sufficient accuracy to distinguish between varying pressures on various parts of an animal's foot and because of this have not been used to so do.
Heretofore electronic sensing of animal foot pressure on a reactive surface during locomotion has not been too feasible, largely because the devices in common use for so doing--piezoelectric crystals or ceramic devices--were relatively large, delicate and particularly susceptible to impact and shock damage. This made such devices difficult to place in a sensory position, so that the results produced would be accurate and required quite complex structures to be associated with such devices to assure their durability and accurate responsiveness. My instant invention seeks to alleviate these problems by providing a relatively small piezoelectric device of low cost and substantial durability to sense pressures on an animal's foot in an instantaneous fashion with extreme accuracy and great reliability.
My invention differs from the prior art by providing a sensing device formed with a plastic piezoelectric sensor having a relatively small areal extent, relative thinness and encapsulation with a metallic shield on the exposed surface to provide substantial durability. The sensing device is small enough that a plurality of them may be positioned on an animal foot, such as the hoof of a horse, to determine pressures simultaneously at a plurality of locations. The sensors may be either temporarily or permanently attached to an animal foot or shoe by adhesion or other mechanical means without in any way changing, damaging or modifying the foot or shoe to which they are attached. The sensor may be quite conveniently incorporated within a structure carried by the foot such as within a human shoe sole or between a metallic shoe and the hoof of a horse. A resilient backing is disclosed to allow sensor positioning over an indentation such as in a horseshoe. The plastic sheet material that constitutes my sensor is easily formed and fabricated, has great reliability and accuracy and provides substantial durability and reliability when properly configured and encapsulated.
The output of one or a plurality of sensors may be analyzed by associating apparatus carried by an animal being sensed or may be amplified and transmitted by ordinary telemetry devices at a distance from the animal. The signal may be recorded, either on or at a distance from the animal, in some physical form and thereafter analyzed to give relative times of various foot actions and to accurately measure pressures upon small areas of a foot. My invention, in providing such structure and functions is distinguished from the prior art individually and in any combination, as hereinafter more particularly set forth.